See this thread
http://subversion.tigris.org/servlets/BrowseList?list=dev&by=thread&from=110741
for details. The basic idea is that this comment in cvs2svn.py is wrong
# Officially, CVS symbolic names must use a fairly restricted set of
# characters. Unofficially, we don't care if some repositories out
# there don't abide by this, as long as their tags start with a letter
# and don't include '/' or '\' (both of which are prohibited by
# official restrictions anyway).
symbolic_name_re = re.compile('^[a-zA-Z][^/\\\\]*$')
because in fact, CVS does allow "/" in symbolic names. SV obviously can't,
since "/" is a path separator and symbolic names become paths in Subversion.
But we could easily convert "/" to one some character not allowed in symbolic
names by CVS. Suggestions in the thread are "." and "," with preference for the
latter because Windows apparently doesn't allow "." at the end of a filename.
I've left this unassigned for the moment. Max, feel free to grab it if you want it.
Bug
Major